Method for monochlorinating paraffins



United States Patent 3,505,418 METHOD FOR MONOCHLORINATING PARAFFINS John C. Jubin, Jr., Wallingford, Pa., assignor to Atlantic Richfield Company, New York, N.Y., a corporation of Pennsylvania No Drawing. Filed Mar. 8, 1966, Ser. No. 532,576 Int. Cl. 'C07c 17/10 US. Cl. 260-660 2 Claims ABSTRACT OF THE DISCLOSURE Chlorinating C to C straight chain paraflins to produce a chlorinated product containing at least 90 weight percent monochloroparaffins by introducing the parafiins into a primary reaction zone together with sufficient gaseous chlorine such that the mixture passes through the primary reaction zone at a linear velocity in the range of from 32 feet per second to 80 feet per second and passing the efiiuent from the primary reaction zone through a secondary reaction zone at a linear velocity less than the linear velocity in the primary zone.

This invention relates to a method for chlorinating straight chain paraffins to produce a chlorinated product containing at least 90 weight percent monochlorinated parafiins.

In recent years the detergent industry has required that the detergents be bio-soft, i.e. that they be readily biologically degradable in order to prevent excessive pollution of streams and underground waters. It has been found that alkyl aryl sulfonates, wherein the alkyl group attached to the aromatic nucleus is straight chain or is only slightly branched, are bio-soft as compared with alkyl aryl sulfonates wherein the alkyl group is highly branched. A convenient method of preparing the straight chain alkyl aryl sulfonates involves monochlorinating a straight chain paraifinic hydrocarbon, alkylating benzene with the chlorinated parafiin and thereafter sulfonating the alkyl aromatic.

In accordance with this invention a method now has been found for monochlorinating straight chain parafiins to produce a chlorinated product which contains at least 90 weight percent of the desired monochloroparaffins. A highly monochlorinated product is desirable for alkylation purposes since diand polychlorinated products give undesirable. alkylation products, i.e. higher molecular weight alkylated products, which so-called heavy alkylate is not suitable for producing water-soluble alkyl aryl sulfonates.

It is an object of this invention, therefore, to provide a method for chlorinating straight chain paraflins to produce high yields of the monochlorinated straight chain parafiins in the chlorinated product.

It is another object of this invention to provide a method for chlorinating straight chain parafiins wherein the velocity of the reactants through the reaction zone is controlled to produce a chlorinated product which contains at least 90 weight percent of the monochlorinated straight chain parafiins.

Other objects of this invention will be apparent from the following description and from the claims.

In accordance with this invention straight chain paraffins in the molecular weight range which are suitable for providing alkylated benzene sulfonates having the desired detergency properties in aqueous media are utilized as the charge material. In general, these paraffinic hydrocarbons which are suitable contain from 8 to 16 carbon atoms in the molecule. Although the parafiinic hydrocarbon charge may contain small amounts of branched chain paraffins, in general these compounds react with chlorine at a faster rate than the rate for the straight chain parafiins, with the result that the product will be contaminated with chlorinated branched-chain paraifins which, as has been pointed out, produce detergents which are not bio-soft. Accordingly, the amount of branched chain paraflins should be as small as possible, i.e. less than 5 weight percent of the total paraffin charge and preferably less than 1 to 2 percent.

The straight chain parafiin charge together with gaseous chlorine is introduced into an elongated reaction chamber which consists of a primary reaction zone followed by a secondary reaction zone. Preferably, the primary reaction zone consists of a pipe having a diameter suitable for the throughput desired, connected to a secondary reaction zone which also consists of a pipe but having a larger diameter than the diameter of the primary reaction zone.

The paraffins and chlorine are introduced into the primary reaction zone at a temperature in the range of from about 225 F. to 250 F. and preferably at a temperature of from 230 F. to 240 F. with the paraffin to chlorine mole ratio being in the range of from about 6:1 to 10:1 with from 7:1 to 8:1 being preferred. The paraffins and chlorine are also introduced into the primary reaction zone at a rate such that they pass through the zone at a linear velocity of at least 32 ft./sec. up to about 80 ft./sec. The primary reaction zone should be of sufficient length to permit a residence time for the paraffins and chlorine of from /2 to 1 second. It will be understood that the reaction zone need not be a pipe which is straight throughout its length but, in accordance with conventional engineering practice, it may be serpentine, i.e. having straight sections with return bends in the manner of steam boiler tubes for example.

The chlorine may be introduced into the primary reaction zone into the stream of paraffin through a nozzle or a plurality of nozzles with the flow rate of the chlorine and the flow rate of the paraffins being adjusted to produce the desired 32 ft./sec. linear velocity in the primary reaction zone. Under these conditions it has been found that there is turbulent flow in the reactor such that from weight percent to weight percent of the chlorine is reacted in the primary reaction zone and that at these velocities the monochloroparaffins in the chlorinated product will exceed weight percent of such product.

The efiluent from the primary reaction zone is passed into the secondary reaction zone which also consists of an elongated zone in the form of a pipe having a diameter larger than the diameter of the primary reaction zone, with turbulent flow being maintained in this section of the reactor. The larger diameter lowers the velocity of the stream and thereby reduces the required chlorine pressure at the inlet to a reasonable and economical level. In general, a chlorine pressure of psi. before it is passed through the nozzle or nozzles is sufficient such that after passing through the nozzle or nozzles a pressure of from 20 to 40 psi is obtained. It will be understood, however, that the nozzle design and configuration as well as the number of nozzles utilized for introducing the chlorine may be varied, and accordingly, the pressures required also will vary in accordance with the particular equipment utilized.

The secondary reaction zone is of such a length that the overall contact time in both the primary and secondary reaction zones is in the range of from about 2 /2 to 3 seconds. Since turbulent flow is also maintained in the secondary reaction zone, most of the remaining chlorine reacts and the effluent from the secondary reaction zone is then passed into the liquid phase of a conventional liquid-vapor separator. Any small amounts of chlorine remaining unreacted after the secondary reaction zone are reacted in the separator and the separator is utilized to separate the HCl gas produced in the reaction from the liquid products, i.e. the chlorinated parafiins and unreacted paraflins. The chlorinated paraflins are thereafter utilized to alkylate benzene for detergent production.

As has been pointed out the most desirable ranges for the reaction condition are temperatures in the range of from 230 F. to 240 F. with parafiin to chlorine mole ratios in the range of from about 6:1 to :1 preferably from 7:1 to 8: 1. At these high molar excesses of paraffin over chlorine, substantially all of the chlorine is reacted and from about 9 to about 14 weight percent of the paraffins are converted to chlorinated products.

Laboratory runs were carried out wherein the chlorine was simply bubbled through a liquid body of the paraffins and it was found that as the ratio of chlorine to parafiin was increased the conversion of the paraflins to chlorinated products increased but the percentage of monochlorinated parafiins in the chlorinated product decreased as the conversion of the paraffins increased. Similar results were found in the laboratory when a mixture of paraflins and chlorine was passed through a tubular glass reactor having a diameter of 1 mm.

In plant scale the linear velocity of the reactants, i.e. the paraffins and chlorine through the tubular reaction zone is controlled by the chlorine flow. Thus, if the amount of chlorine employed was sufiicient only to give a relatively low velocity of the reactants through the reaction zone, as would be expected, the amount of paraffins converted was also low since the chlorine to paraffin ratio was low. It was found quite unexpectedly however, and contrary to the laboratory findings, that as the ratio of chlorine to paraffin was increased, i.e. the velocity through the tubular reactor was increased and thus the amount of paraftins converted was increased, that the monochloroparaffin selectivity increased, i.e. the percentage of monochlorinated paraflins in the chlorinated product increased. In summary, in the laboratory as the paraffin conversion increased the monochloroparafiin selectivity decreased, while in the plant scale runs as the paraflin conversion increased, i.e. the linear velocity of reaction increased, the monochloroparaffin selectivity increased. Thus the critical process variable was the linear velocity of reactants through the primary reaction zone and if the linear velocity of the reactants through the primary reaction zone was at least 32 ft./sec. and ranging up to about 80 ft./sec. a monochloroparaffin selectivity of 90 percent or higher was obtained, i.e. that 90 weight percent or more of the chlorinated product was the monochlorinated parafiin fraction.

In order to demonstrate the criticality of the linear velocity of the reactants through the primary reaction zone several runs were carried out. In each run a charge stock consisting essentially of straight chain paraflins (i.e. less than about 1 weight percent of non-straight chain paraflins) having from 8 to 16 carbon atoms in the molecule was charged to the primary reaction zone at an mlet temperature of 230 F. to 240 F. and at a constant flow rate determined by the capacity of the equipment. The prim ry eac ion zone was a pipe having an inside diameter of approximately 3 inches and a length of approximately 40 feet. The secondary reaction zone was a pipe having an inside diameter of approximately 4 inches and a length of approximately 110 feet.

In the first run an amount of chlorine was utilized Such that the linear velocity of the mixture of parafiins and chlorine was maintained at about 15 ft./sec. A paraffin conversion of 4.25 weight percent was obtained with a 79 weight percent selectivity, i.e. 79 weight percent of the chlorinated products were monochlorinated paraffins.

In a second run the amount of chlorine was adjusted such that a linear velocity of the reactants through the primary reaction zone was about 29 ft./sec. A parafiin conversion of 8.3 weight percent was obtained together with a monochloroparafiin weight percent selectivity of 87.5.

In a third run the amount of chlorine was adjusted such that a 32 ft./sec. linear velocity through the primary reaction zone for the reactants was obtained. A paraffin conversion of 9.25 weight percent with a monochloroparaffin weight percent selectively of 90 weight percent resulted from operating under these conditions.

In a fourth run the linear velocity of the reactants through the primary reaction zone was 44.5 ft./sec. and the paraffin conversion was 12.75 weight percent. The amount of monochlorinated parafiins in the chlorinated product was 91 weight percent.

These runs demonstrate the criticality of utilizing a linear velocity of the parafiin and chlorine through the primary reaction zone of at least 32 ft./sec. In these runs it was found that a residence time in the primary reaction zone of from /2 to 1 second with a total residence time of from 2 /2 to 3 seconds in the primary and secondary reaction zones gave substantially complete conversion of the chlorine. In a few instances small amounts of unreacted chlorine passed into the liquidvapor separator where the reaction of the chlorine was completed. These amounts were not significant, generally less than 1 to 2 percent of the charge amount of chlorine.

It also will be understood that the temperatures which have been set forth are inlet temperatures for the primary reaction zone. Since the reaction is exothermic temperatures of from 300 F. to 320 F. are frequently found at the outlet of the secondary reaction zone.

Iclaim:

1. A method for chlorinating straight chain parafllns having from 8 to 16 carbon atoms in the molecule to produce a chlorinated paraffin product wherein the monochloroparaffins constitute at least 90 weight percent of said chlorinated parafiin product, which comprises introducing said parafiins into a primary reaction zone together with sufiicient gaseous chlorine such that the mole ratio of said paraflins to chlorine is in the range of from 6:1 to 10:1 and such that the parafiin and chlorine mixture passes through said primary reaction zone at a linear velocity of at least 32 ft./sec. and ranging up to ft./sec., said paraflins and gaseous chlorine being introduced into said primary reaction zone at a temperature in the range of from about 225 F. to 250 F., passing the effluent from the primary reaction zone directly into and through a secondary reaction zone at a linear velocity less than the linear velocity in said primary reaction zone, the time required for the mixture of said parafiins and gaseous chlorine to pass through said primary reaction zone being in the range of from /2 to 1 second and the total time required to pass through said primary and said secondary reaction zone being in the range of from 2 /2 to 3 seconds, and recovering the chlorinated reaction product from said secondary reaction zone.

2. The method according to claim 1 wherein the mole ratio of paraflins to gaseous chlorine is in the range of from 7:1 to 8:1 and the paraffins and gaseous chlorine are introduced into the primary reaction zone at a temperature in the range of from 230 F. to 240 F.

References Cited UNITED STATES PATENTS Sievers 260-660 X Ray et a1. 260660 X Luberoff 260- 660 X Feighner et a1. 260-660 X 5 LEON ZITVER, Primary Examiner JOSEPH A. BOSKA, Assistant Examiner 

